In FIG. 1 a General Packet Radio Service (GPRS) network is depicted. The network depicted in FIG. 1 is further described in the Third Generation Partnership Project (3GPP) specification TS 23.060.
In order to provide encrypted communication between the mobile station and the cellular radio network encryption of the user plane on the Logical Link Control (LLC)-layer is provided. The network Logical Link Control (LLC) entity is located in the Serving GPRS Support Node (SGSN) and in the mobile station (MS). In FIG. 2, a view illustrating different entities and the corresponding interfaces in a GPRS network is shown. FIG. 2 depicts a Mobile Station (MS) connected to a Base Transceiver Station (BTS) of a GPRS network over a Um interface. The BTS is in turn connected to a Base Station Controller (BSC) over an Abis interface. The BSC is connected to SGSN over a Gb interface. For completeness FIG. 2 also shows that the SGSN is connected to a Gateway GPRS Support Node (GGSN) over a Gn interface and the GGSN is connected to the internet over a Gi interface.
In FIG. 3a the user plane protocol architecture in accordance with 3GPP TS 23.060 is depicted. FIG. 3b depicts (also in accordance with 3GPP TS 23.060) the control plane protocol architecture between MS and SGSN for the case of A/Gb-mode.
Further FIG. 4 shows the relative positioning of the Sub-Network Dependent Convergence Protocol (SNDCP) and LLC layers. The conveyance of Network Packet Data Units (N-PDUs) using the SNDCP/LLC protocol stack is performed as follows:                For the downlink case an N-PDU essentially consists of an application layer data packet to be delivered to a mobile station. Upon reception of an N-PDU the SNDCP layer applies compression (if needed) and then disassembles the resulting compressed packet into multiple Sub-Network PDUs (SN-PDUs) depending on configuration parameters that determine the maximum size of Logical Link PDUs (LL-PDUs). The SN-PDUs are passed to the LLC layer which then maps each SN-PDU into an LL-PDU, applies ciphering to each LL-PDU (if necessary), transmits the LL-PDUs to the BSS using the BSSGP transport layer and the BSS then transmits the LL-PDUs to the mobile station using the Radio Link Control (RLC) layer. Each received LL-PDU is unciphered (if ciphered) by the LLC layer at the mobile station and the SN-PDU contained therein is extracted and sent to the SNDCP layer. The SNDCP layer reassembles a set of one of more SN-PDUs to create an N-PDU and then decompresses the N-PDU (if compressed) to produce the original application layer data packet.        For the uplink case an N-PDU available for transmission at the mobile station is disassembled as described for the downlink case and the resulting LL-PDUs are transmitted from the mobile station to the Base Station Subsystem (BSS) using the RLC layer. The BSS relays each LL-PDU to the SGSN where the original N-PDU is recovered as described for the downlink case.        
There is a constant desire to improve the performance in cellular radio networks and to improve the speed by which a mobile station within the cellular network can access information nominally provided by servers located in the data network.
Hence there exists an ongoing need for developing new methods and devices providing improved GPRS system operation as perceived by users of this service.